A dog’s fitness is a combination of many factors including their cardiorespiratory function, balance, strength, flexibility, proprioception, muscle strength, and stamina.

Stamina is defined as the dog’s “ability to withstand high energy – demanding activity over extended period of time”. There are many factors that influences a dog’s stamina. These factors can be intrinsic to the dog, environmental or fixed factors such as breed, age, and sex.

Factors that are intrinsic to the dog include muscle activity, fat and electrolyte metabolism, body weight, and level of conditioning / training.

Environmental factors that affect stamina may include ambient temperature and humidity.

Conditioning a dog to perform at the required fitness level and acclimatizing them to the environment in which they will perform has an effect of the dog’s stamina.

When dogs exercise, they exert energy which generates heat. Canine athletes, because of the demands of their “work” have higher cardiovascular and thermoregulation demands than pet dogs. Canine athletes therefore have greater internal body temperatures and cardiac regulation ability. When exercising cardiac output can increase by 74 – 200% and carotid blood flow increases by up to 500%. These are heat tolerance strategies that increases the blood flow throughout the body and ensures maximal heat exchange.

When exercising, dogs limit evaporative loss from panting which leads to the following physiological conditions:

• Abnormally rapid breathing

• Lactic acidosis – accumulation of lactate

• Respiratory alkalosis – increased respiration elevates blood pH and leads to a disruption in the acid – base balance in the body

• Body temperature rises above normal ranges

• Increased heart rate

• Reduced carbon dioxide in the blood

When the extent of these physiological changes exceeds the dog’s fitness level or conditioning, then the dog’s ability to exercise for long periods diminishes and their need for more regular rest periods increases.

Study objective

A study of working dogs investigated the factors that influences exercise stamina in regularly exercised dogs.

Participants

The study included 12 regularly exercised dogs – eight males and four females from five different breeds. Their ages ranged from 8 – 23 months. The dogs had previous training in retrieving and various agility / search tasks.

Study design

The study involved the dogs participating in a 30 minute exercise challenge on five separate days over a 19 day period.

There were two study periods with dogs selected randomly and assigned to a study period. The study periods were in June – July and August.

The exercise period commenced at 12 noon on each study. It started with 5 minute pre-exercise routine comprising trotting and active stretches.

The exercise challenge involved the following:

• 5 minutes search – alerting on 2-3 scent sources

• 5 minutes rest in the shade, on lead with the trainer standing stationery. The dog could move around to the length of the lead.

• 5 minutes agility – climbing elevated ladders, walking on unstable surfaces, cavalettis, distance exercises and tunnels

• 5 minutes rest in the shade

• 5 minutes ball retrieve

• 5 minutes rest in the shade

The exercise challenge was followed by a 5 minute post-exercise, warm down session comprising light trotting and walking.

Exercise was ceased if the dog showed any signs of fatigue such as curled tongue while panting, seeking out shade or reluctance to work. For consistency, a single trainer determined when a dog should stop exercising for the purpose of the study.

Physiological measurements were taken between 7am and 9am on exercise days and immediately after the exercise period.

Measurements included the following:

• Body temperature – Core body temperature, left and right ear temperature

• Pulse rate

• Venous blood measured for pH, gases, electrolytes, base excess in extracellular fluid compartments, glucose, haemoglobin, haematocrit and blood lactate

• Locomotor activity – attached to the dogs’ collar from 8am – 10am on exercise days. The device measured activity in 1 minute increments and included warm up, exercise and warm down periods.

Study results

Over the two study periods the median ambient temperature was 28.7 degrees Celsius and the median humidity was 49.6% however there was a significant difference in humidity between the two periods: first period humidity was 50% and second, it was 40%.

The mean exercise period was 27.1 minutes.

The study shows that the following influenced dogs’ stamina:

• Pre-exercise activity

• Post-exercise activity

• Outdoor temperature

• Reduction in base excess (amount of H+ ions required to restore acid – base balance) and TCO2 (Total carbon dioxide in the blood.)

As stamina increases, the two biomarkers: base excess and TCO2 decrease.

The study also found increases in glucose and haematocrit post exercise. Increases in glucose is a response to physical stress such as exercise. Likewise, increases in haematocrit is commonly associated with acute vs endurance exercise as it facilitates the blood’s oxygen carrying capacity.

In terms of external factors like temperature and humidity, the study found that as outdoor temperature increased, stamina decreased. In this study, humidity did not have an effect on stamina.

A predictor of stamina was the dogs’ pre and post exercise activity. It was found that those dogs with higher pre and post exercise activity levels also had increased stamina.

A possible explanation for this finding is that pre-exercise warm up increases the temperature of joints and muscles and lubricates the fascia which plays a role in injury prevention and increases muscle contraction and relaxation speeds. Post-exercise, warm down ensures that blood continues to circulate to the muscles and contributes to removal of metabolic waste.

Finally, the study found that core body temperature did not influence the dogs’ stamina but rather their ability to dissipate heat. In the working dogs in this study, their core body temperatures was as high as 42.4 degrees Celsius. Typically, core body temperatures above 40.6 is defined as heat stroke however none of the dogs in the study exhibited symptoms of heat stroke or injury. The study concluded that as these dogs were conditioned to work in hot conditions, they were acclimated to exercising with elevated core body temperature. Further, in all dogs in the study, their body temperatures rapidly returned to normal ranges without intervention after exercise.

Take away messages for dog owners

There are two strong messages to take from this study for all dog owners whether your dog is involved in dog sports or not.

Firstly, a good pre and post exercise warm up and warm down routine can contribute to the dog’s ability to perform. The dogs in this study with the highest activity levels i.e. amount of movement in their pre and post exercise session, also demonstrated the greatest stamina in the exercise challenge. Including walking, trotting and active stretching to a warm up and warm down routine can contribute to a dog’s performance, prevent injury and aid recovery from a strenuous session.

Secondly, allowing the dog to acclimatise to both the exercise requirements and the environment in which they need to perform is critical for building a dog’s stamina.

Training or conditioning has two parts. Firstly, train the dog in the performance required with consideration for skills, duration and intensity e.g. running next to you on lead at 6km/ hour for 20 minutes.

Secondly, condition the dog to perform in the environmental conditions e.g. ambient temperature of up to 27 degrees Celsius and 90% humidity.

For more information on conditioning and injury prevention you might also like:
https://www.fullstride.com.au/blog/repetitive-strain-injury-in-dogs-and-how-to-treat-it

https://www.fullstride.com.au/blog/is-it-too-hot-to-walk-my-dog-how-exercising-in-the-heat-affects-dogs

http://www.fullstride.com.au/blog/is-chasing-a-ball-bad-for-dogs

https://www.fullstride.com.au/blog/muscle-injury-symptoms-in-dogs

Until next time, enjoy your dogs.

Source:

Robbins, P.J, Ramos, M.T, Zanghi, B.M, and Otto, C.M. 2017 “Environmental and physiological factors associated with stamina in dogs exercising in high ambient temperatures” Frontiers in Veterinary Science, Vol 4, September 2017.